The meal having been served in this beautiful Oriental manner, the Lord asks, “Where is Sarah?” Abraham made answer, “Behold, in the tent.” Then the Angel of the Lord, not only renews the promise, but that it should be fully realized in the birth of Isaac within a year. Sarah, behind the tent door, hears this unqualified assurance, but, viewing it from nature’s standpoint, rendered doubly improbable from her life-long barrenness, “laughed within herself.” We can not regard this as a laugh of unbelief, or the scoff of doubt, as some do, but as a laugh falling short in her conception of God. The thing which was impossible according to the established laws of nature, her faith had not yet grasped as being possible with God. But the Lord, nevertheless, observed Sarah’s laugh, and this divine hearing on the part of the Angel of the Lord, startled her, and had its part in the strengthening of her faith. It prepared the way for the question, “Is anything too hard for the Lord?” To her own mind one thing, namely, that she should be a mother at ninety years of age, seemed too hard. And so the question had to do with this very thought, and must be settled on the side of her faith. And she grandly and heroically asserted her belief that nothing, not even the seeming insurmountable obstacle which nature interposed, was too great for God to overcome, and her faith was strengthened, for we read, “through _faith_ Sarah received strength to conceive seed, and was delivered of a child when she was past age, because she _judged_ Him faithful who had promised” (Heb. xi, 11). The trial of her patience of faith was a long struggle. It took twenty-five years to bring her up to the point where her faith could grasp the truth that nothing was too hard for the Lord to perform. But this blessed woman at length stood in right relation to God, for, without faith, be it observed, it is impossible to please God, or to receive anything at His hands. In due time Isaac was born. It was the great event in Sarah’s life. As the mother looked down into the face of the son of her bosom she breaks forth in an exultant song of thankfulness, not unlike that of Mary, the blessed virgin. The little song of Sarah, it has beautifully been said, is the first cradle hymn. Our Lord reveals the profoundest source of this joy, when, in addressing the Pharisees, who held Abraham to be their father, said, “Your father Abraham rejoiced to see my day.” Sarah, in the birth of Isaac, is the ancestress of Christ. Spiritually viewed, the birthday of Isaac becomes the door or entrance of the day of Christ, and the day of Christ the background of the birthday of Isaac.